Double-pass Spray Chamber Research Articles

Design, Optimization, and Application of a 3D-Printed Polymer Sample Introduction System for the ICP-MS Analysis of Nanoparticles and Cells

Commonly used sample introduction systems for inductively coupled plasma mass spectrometry (ICP-MS) are generally not well-suited for single particle ICP-MS (spICP-MS) applications due to their high sample requirements and low efficiency. In this study, the first completely 3D-printed, polymer SIS was developed to facilitate spICP-MS analysis. The system is based on a microconcentric pneumatic nebulizer and a single-pass spray chamber with an additional sheath gas flow to further facilitate the transport of larger droplets or particles. The geometry of the system was optimized using numerical simulations. Its aerosol characteristics and operational conditions were studied via optical particle counting and a course of spICP-MS measurements, involving nanodispersions and cell suspensions. In a comparison of the performance of the new and the standard (quartz microconcentric nebulizer plus a double-pass spray chamber) systems, it was found that the new sample introduction system has four times higher particle detection efficiency, significantly better signal-to-noise ratio, provides ca. 20% lower size detection limit, and allows an extension of the upper limit of transportable particle diameters to about 25 µm.

Infrared heating of commercially available spray chambers to improve the analytical performance of inductively coupled plasma optical emission spectrometry

Heating a Scott double-pass spray chamber with two ceramic block heaters improves detection limits 10-fold on average.

Comparison of a high temperature torch integrated sample introduction system with a desolvation system for the analysis of microsamples through inductively coupled plasma mass spectrometry

This work describes for the first time the comparison of the analytical performances obtained with a high temperature torch integrated sample introduction system (hTISIS) against those found with a commercially available desolvation system (APEX) associated with inductively coupled plasma mass spectrometry (ICP-MS). A double pass spray chamber was taken as the reference system. Similar detection limits and sensitivities were obtained in continuous injection mode at low liquid flow rates for the APEX and hTISIS operating at high temperatures. In contrast, in the air-segmented injection mode, the detection limits obtained with hTISIS at high temperatures were up to 12 times lower than those found for the APEX. Regarding memory effects, wash out times were shorter in continuous mode and peaks were narrower in air segmented mode for the hTISIS as compared to the APEX. Non spectral interferences (matrix effects) were studied with 10% nitric acid, 2% methanol, for an ICP multielemental solution and a hydro-organic matrix containing 70% (v/v) acetonitrile in water, 15mmolL−1 ammonium acetate and 0.5% formic acid containing lanthanide complexes. In all the cases, matrix effects were less severe for the hTISIS operating at 200°C and the APEX than for the double pass spray chamber. Finally, two spiked reference materials (sea water and Antartic krill) were analyzed. The hTISIS operating at 200°C gave the best results compared to those obtained with the APEX and the double pass spray chamber. In conclusion, despite the simplicity of the hTISIS, it provided, at low liquid flow rates, results similar to or better than those obtained with the by other sample introduction systems.

Study of a direct current atmospheric pressure glow discharge in helium with wet aerosol sample introduction systems

In this study a He DC atmospheric pressure glow discharge (APGD) is characterized under dry conditions and with the introduction of wet aerosols. The aerosols are generated by a conventional pneumatic nebulization system using a MicroMist nebulizer placed in a double pass spray chamber according to Scott or alternatively by a custom-built drop-on-demand (DOD) system based on printer cartridges. The experiments are performed at a He gas flow of 500 mL min−1 and 40 mA current. The influences of the H2O load on the discharge rotational temperature (Trot), excitation temperature (Texc) and the electron number density (ne) are determined. Temperature reductions when comparing dry and wet conditions are found to be around 500 K for the Trot and 240–400 K for the Texc. Detection limits for the elements Cd, Cu, Mg, Mn and Na are presented for pneumatic nebulization coupled to a continuous flow injection system. They are found to be between 10 μg L−1 for Na and 140 μg L−1 for Cu. In the case of the drop-on-demand system a value of 16 μg L−1 for Na was obtained. The applicability of the discharge to the determination of Na in a tap water sample at concentration levels of 20 mg L−1 is shown for both introduction systems and the accuracy of the results is found to be within 1.3 mg L−1 as compared to the result of inductively coupled plasma optical emission spectrometry (ICP-OES).

Determination of uranium and selected elements in Polish dictyonema shales and sandstones by ICP-MS

Inductively coupled plasma mass spectrometry was used for characterization of Polish dictyonema shales and sandstones as a potential source of uranium and other technologically important elements. Influence of sample digestion of these materials for the determinations: U, Th, Cu, Co, Mn, Zn, La, V, Yb, Mo, Ni, Sb and Fe has been tested. The method involved two-step microwave acid digestion, followed by direct determination by ICP-MS. The instrument used for all determinations was ELAN DRC II (Perkin Elmer) with crossflow nebulizer with Scott double-pass spray chamber and Ni cones. Certified Reference Materials were used as a quality control standard to validate the applied analytical procedure. The expanded measurement uncertainty U (k = 2) ranged from 5 to 15 %, in dependence on the element. The obtained results provided information on the contents of minor and trace elements in shales and sandstones depending on their origin. At this moment, these geological deposits can be treated as a potential source of raw elements.

Speciation Analysis of Organotin Compounds in Sediment by Hyphenated Technique of High Performance Liquid Chromatography-Inductively Coupled Plasma Mass Spectrometry

A hyphenated technique of high-performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (HPLC-ICP-MS) was applied to the simultaneous determination of five organotin compounds in the sediment samples. Agilent TC-C18 column was selected; mobile phase of the HPLC was CH3CN:H2O-CH3COOH(65:23:12, V/V), 0.05% TEA, pH 3.0 at flow rate 0.6 mL min−1, and 30% O2/Ar mixed gas was added to the make-up gas, which not only reduced the carbon buildup on the cones but also protected the cones. To reduce solvent loading on the plasma, the double-pass spray-chamber was peltier cooled to −5 °C. The high RF power (1500 W) helped the samples to decompose completely. A mixed standard solution of five mixed organotin compounds from 100 μg L−1 to 1 μg L−1 was used for the method assessment. The results indicate that the correlation coefficient of calibration curves (R2) for each organotin compound was over 0.998. The international standard reference PACS-2 samples were treated by supersonic extraction with mobile phase added 0.2% tropolone. Two organotin compounds including dibutyltin (DBT) and tributyltin (TBT) were detected with this method. The values of dibutyltin (DBT) and tributyltin (TBT) were 0.99 mg kg−1 and 0.83 mg kg−1, respectively. The results showed good accordance with the certified values. The recoveries from the standard addition for five organotins were over 80%.

Internal standardization with yttrium spectral lines using axial-viewing inductively coupled plasma atomic emission spectrometry for plant certified reference materials analysis

The performance of yttrium as internal standard was investigated when aspirating digested samples or alternatively slurries of certified plant reference materials. The stability of the yttrium signal used for analyte signal normalization was examined for three ionic emission lines of yttrium. The results showed that the use of yttrium was beneficial; however for the slurry sample introduction technique it was not equivalently efficient in terms of overall recovery. In this case, the employment of a cyclonic instead of a double-pass spray chamber in combination with yttrium internal standardization leads to quantitative recoveries of the analytes.

Effect of the silicon chemical form on the emission intensity in inductively coupled plasma atomic emission spectrometry for xylene matrices

Silicon is present in petrol products under very different chemical forms. The effect of the silicon chemical form on the sensitivity was studied by inductively coupled plasma atomic emission spectrometry (ICP-AES). Solutions containing sixteen different silicon organic compounds with the same silicon concentration were prepared in xylene. The studied compounds were: six siloxanes, nine silanes and a silicate. Their boiling points ranged from 101 °C (hexamethyldisiloxane) to 310 °C (2,3,4-(epoxycyclohexyl)ethyltrimetoxysilane). The results indicated that the ICP-AES signal depended strongly on the silicon compound. Thus, for a commonly used sample introduction system consisting of a cross-flow pneumatic nebulizer coupled to a Ryton double pass spray chamber, the signal varied by a factor of up to 17, depending on the compound. For most studied cases, some siloxanes yielded higher emission intensities than silanes. In addition, under some circumstances, hexylmethyldichlorosilane and dimethyldodecylchlorosilane also produced higher signals than the other studied silanes. In order to elucidate the possible mechanisms for these changes, a series of experiments was performed to verify whether the origin could be assigned either to the plasma or to the sample introduction system. Using the Mg II/Mg I ratio, no significant change in the plasma characteristics was actually observed. As regards the sample introduction system, (i) the primary aerosol, (ii) the transport and memory effects using continuous and discrete introduction modes, an alternative spray chamber, and a total consumption system (the TISIS system), and (iii) the tertiary aerosol, via an impactor, were studied. Additional experiments were carried out with an ultrasonic nebulizer. In addition, the Si behaviour was compared to other elements, such as Cu, Mg, Mn and Zn. The results indicated that the Si behaviour was not related to the pneumatic nebulizer and suggested that a fraction of silicon was transported towards the plasma as a vapour when it was present as hexamethyldisiloxane (i.e., the compound with the lowest boiling point among the species studied). In any case, the variability of the signal induced by the different silicon chemical forms was less significant for the TISIS than for cyclonic and ultrasonic nebulizer. The observed results were specific to silicon as the signal of the other elements did not significantly change with silicon chemical form. As a consequence, internal standardization was not appropriate for mitigating interferences on silicon when petroleum products were analyzed.

A new demountable hydrofluoric acid resistant triple mode sample introduction system for ICP-AES and ICP-MS

A new sample introduction system with a triple mode function was developed by modifying a commercially available cyclonic spray chamber and combining it with a commercial parallel path nebulizer. The system can be used for nebulization only, vapor generation (hydride or cold vapor) only and both together (dual mode). The introduction system is very practical in use, as it can be dismantled from the bottom side and all the inserts can be removed and cleaned easily after the end of analysis. Unlike another commercial multimode system, this new one is HF-resistant and can be used with all acids. The analytical performance of the new HF-resistant triple mode sample introduction system (HFR-TMSIS) was studied by coupling it with ICP-AES and ICP-MS and comparing the performance with the conventional single mode HF-resistant sample introduction systems: i.e. a V-groove nebulizer with Sturman–Masters spray chamber for ICP-AES and cross flow nebulizer with double pass spray chamber for ICP-MS. The performance of the new system was studied using the various modes, determining As, Cd, Cu, Fe, Mn and Pb using ICP-AES and Cd, Cu, Hg and Pb using ICP-MS. In the first case NaBH4 was used for hydride generation (of As), and in the second case SnCl2 was used for generation of cold vapor (Hg). For both ICP-AES and ICP-MS, the use of HFR-TMSIS improved the analytical performance of both As and Hg in hydride and cold vapor generation mode, respectively, and also in the dual mode compared to the conventional single mode systems. For the other elements the figure of merits of nebulization and dual mode were comparable with the conventional systems. Cold vapor generation mode (for the determination of Hg) and dual mode (for simultaneous determination of cold vapor of Hg together with other elements) were used for the analysis of various CRMs (digested with HF + HNO3 + H2O2 or HNO3 + H2O2) by ICP-MS.

Development of a slurry introduction method for multi-element analysis of antibiotics by inductively coupled plasma atomic emission spectrometry using various types of spray chamber and nebulizer configurations

A direct sample introduction inductively coupled plasma atomic emission spectrometric (ICP-AES) method, for multi-element analysis of powdered antibiotic drugs was developed using the slurry formation technique. The slurry of powdered sample is formed in dilute nitric acid solution in presence of Triton X-100 surfactant. Two different configurations of spray chamber and nebulizer were tested for direct aspiration of slurry into the plasma: (i) cyclonic spray chamber combined with babington-type nebulizer and (ii) scott-type double-pass spray chamber combined with cross-flow nebulizer. The latter configuration proved to be less tolerable to slurry aspiration. RF power generator, nebulizer argon gas flow rate, nebulizer sample uptake flow rate and slurry sample concentration were optimized. The sensitivity of the proposed method was compared to the corresponding sensitivity obtained from aqueous solutions for each analyte. The performance characteristics of the slurry aspiration method were evaluated against the complete acid-digestion method followed ICP-AES. Finally, the proposed method was applied to the analysis of commercial antibiotics.

Development of a rapid multi-element method of analysis of antitussive syrups by inductively coupled plasma atomic emission spectrometry and direct sample introduction

A new rapid method was developed and optimized for routine multi-element determination of traces of metals in antitussive syrups using direct introduction of diluted syrup into the nebulization system of inductively coupled plasma atomic emission spectrometer (ICP-AES). Using a Scott-type double-pass spray chamber combined with a cross-flow nebulizer, the optimum ICP conditions, like RF incident power, argon gas flow rate and nebulizer sample uptake flow rate were found. A critical objective of the study was to evaluate the matrix effect on the intensity and consequently on the sensitivity of the developed method. Thus, the maximum syrup concentration which could be introduced into the argon plasma, was estimated. The sensitivity variation was calculated as compared to the corresponding sensitivity obtained from aqueous solutions for each analyte. The performance characteristics of the proposed method were evaluated for quantitative and semi-quantitative determination and finally, the method was applied to the analysis of various commercial antitussives.

A microwave assisted desolvation system based on the use of a TM010 cavity for inductively coupled plasma based analytical techniques

A new microwave assisted desolvation system based on the use of a TM010 cavity (MWDS2) has been developed and evaluated in plasma based analytical techniques: inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). The new design overcomes the main experimental drawbacks shown by previous designs based on the use of domestic ovens: (i) lack of control on microwave generation and application; and (ii) inappropriate MW cavity characteristics. The evaluation has been performed in terms of the effect of the incident microwave power and the sample uptake rate and the results obtained has been compared with those afforded by a conventional sample introduction system (nebulizer and double pass spray chamber) and a desolvation system based on the use of a domestic microwave oven (MWDS). The new MWDS2 give rise to higher analytical signals and lower limits of detection and stabilization times (2–3 times) than those obtained with the MWDS in ICP-AES and ICP-MS.

Compensation for matrix effects in ICP-AES by using air segmented liquid microsample introduction. The role of the spray chamber

The combination of sample injection into an air carrier stream (i.e., air segmentation) with a low sample consumption system has been evaluated for the analysis of microsamples through ICP-AES. A PFA micronebulizer has been coupled to: (i), a double pass spray chamber; (ii), a Cinnabar cyclonic spray chamber; and (iii), a torch integrated sample introduction system, TISIS. Three matrices have been studied: in addition to water two concentrated acid solutions (2 mol l−1 nitric acid and 1.7 mol l−1 acetic acid) and Na 5,000 µg ml−1. A simulation of the evolution of the drop size distributions of the aerosols with time was carried out in order to evaluate the extent of solvent evaporation inside the chamber. The total mass of solvent evaporated inside the chamber was estimated and it was concluded that, at 25 °C, about 4–6 s residence time were required to promote the maximum evaporation of the solvent. In order to ensure this, discrete sample introduction into an air carrier stream (i.e., air segmentation) was used. Narrow peaks (i.e., with a full width at half maximum, FWHM, as short as 10 s) were obtained for a 10 µl injected sample. The peaks found for the Cinnabar and TISIS were narrower than those for the double pass spray chamber. More importantly, the interferences caused by inorganic as well as organic matrices were less severe in discrete than in continuous mode. The theoretical simulations allowed explanation of these results in terms of the enhancement of the solvent evaporation both for water and matrices in this operating mode. The enhanced solvent evaporation with respect to the situation in continuous mode minimized differences in analyte transport towards the plasma induced by these compounds. Despite this, in discrete mode a residual matrix effect was found that was attributed to the aerosol transport process. Internal standardization (IS) was applied to transient signals and the interferences were compensated for in virtually all the cases. Good results were obtained for the four emission lines taken as internal standards (i.e., Mg 280.270, Co 228.616, Cr 205.552 and Cu 324.754). However, for acetic acid and a few lines, IS was not efficient for removing interferences. The methodology was validated by analyzing two reference solid samples of foods (i.e., bovine liver and mussel tissue). By using Cd 214.438 as internal standard and under discrete mode 100% recoveries were found.

Study of direct injection in ICP-AES using a commercially available micronebulizer associated with a reduced length torch

The most critical dimensions of an ICP torch are the distance between the outer gas inlet and the top of the intermediate tube, the magnitude of the space left between the two outermost tubes and the overall torch diameter. The reduction in the torch length while keeping constant the critical dimensions allows injecting directly the aerosol generated by a conventional pneumatic concentric micronebulizer into the plasma by simply fitting it at the torch base. This approach is presented for the first time in this paper. A MicroMist has been used in conjunction with the reduced length torch. The new system has been evaluated in terms of ICP-AES sensitivity, signal stability and matrix effects caused by nitric acid. The results have been compared against those provided by a double pass, a low inner volume cyclonic spray chamber (Cinnabar), a torch integrated sample introduction system (TISIS) and a direct injection high efficiency nebulizer (DIHEN). When using the reduced length torch, at the optimum nebulizer liquid and gas flow rates in terms of sensitivity (i.e., 60 μl min−1 and 0.15 l min−1, respectively) the MicroMist generated aerosols with droplets whose diameters were even higher than 100 μm. Therefore, the selection of this nebulizer was based on criteria other than signal stability such as robustness and lack of tip blocking problems. Despite of this, the results were not as different from those afforded by a DIHEN as expected. For the reduced length torch, the maximum signal improvement factor with respect to a double pass spray chamber was from 1.5 to about 3 depending on the liquid flow rate and the emission line. Similar limits of detection were found for both systems. Meanwhile, these ranges were from about 1.5 to 4 and from 1.3 to 7 for the TISIS and DIHEN, respectively. Note that under its optimum operating conditions, the DIHEN generated droplets with diameters above 30 μm. As expected, at low liquid flow rates, wash out times were more than 20 times shorter for the reduced length torch than for a double pass one. As regards the matrix effects, it was found that the two direct sample injection systems tested behaved alike, the interferences becoming more severe as the delivery flow rate went up. A problem found with the MicroMist associated to the reduced length torch was that the signal stability was poorer than for the remaining systems.

Optimization of the evaporation cavity in a torch integrated sample introduction system based ICP-AES system. Applications to matrix and transient effects, analysis of microsamples and analysis of certified solid samples

Results corresponding to the optimization of the aerosol evaporation cavity of the previously published torch integrated sample introduction system (TISIS) are shown in the present work. A micronebulizer (i.e., MicroMist) operated at liquid delivery rates in the 20–200 µl min−1 range was used throughout. Theoretical calculations suggested that the TISIS chamber allowed the evaporation of a significant fraction of the solvent contained in primary aerosol, while the remaining droplets first impacted against its inner walls and then evaporated. The cavity dimensions (i.e., length and inner diameter) were optimized in terms of sensitivity and memory effects. The results demonstrated that the longer the cavity, the higher the sensitivity, whereas an increase in its diameter did not significantly modify the aforementioned parameters. The optimized TISIS cavity, with a conical shaped end, proved to significantly shorten the wash-out times with respect to a double pass spray chamber and a low inner volume cyclonic type one (i.e., a Cinnabar spray chamber). Besides, the TISIS was used for discrete sample introduction of very low sample volumes (i.e., from 0.3 to 32 µl). The peaks found were narrower and higher than those provided by a double pass spray chamber. Matrix effects caused by sodium, acetic acid and ethanol solutions were less severe for TISIS than for the double pass and the Cinnabar spray chambers, while transient effects caused by nitric acid solutions almost disappeared when using the TISIS. As a result of the mitigation of the interferences, the recoveries found for three certified solid samples while calibrating with plain water standards were closer to 100% for the TISIS than for double pass and mini cyclonic spray chambers.

Characterization of a double-pass spray chamber for ICP spectrometry by computer simulation (CFD)

Computational Fluid Dynamics (CFD) is applied to fundamental investigations on the aerosol flow and its modification in spray chambers typically used in ICP–OES spectrometry. Detailed information is gained on the flow field (argon flow), the droplet motion and on the droplet deposition at different places on the walls inside the chamber, which is not accessible experimentally. The temporal course of the calculated mass flow rate at the outlet of a double-pass Scott type spray chamber is compared with an analytical signal received from the ICP spectrometer. The shape of the calculated time-resolved mass flow corresponds well with the shape of the analytical signal. The information on the detailed functions of various types of spray chambers gained by CFD can be used for optimization of their performance.

Study of matrix effects using an adjustable chamber volume in a torch-integrated sample introduction system (TISIS) in ICP-AES

In the present work, the recently designed torch integrated sample introduction system (TISIS) is characterized in terms of ICP-AES analytical figures of merit and matrix effects, and compared with a system dedicated to the analysis of low sample volumes (i.e., a micronebulizer, MicroMist, coupled to a low inner volume cyclonic spray chamber, Cinnabar). A double pass spray chamber was also used as a reference system. The TISIS design was modified with respect to the original in order to adjust the cavity inner volume to the analysis requirements. Four different volumes were tested (5, 9, 15 and 20 cm3). For the two latter ones, a mobile polyethylene body was adapted to the torch base. By modifying the position of this body, the volume of the chamber between the nebulizer and the injector torch could be adjusted. The liquid flow rates tested ranged from 20 to 200 µl min−1. At the lowest Ql studied, the solvent evaporation was very intense and, thus, the TISIS chamber acted as an evaporation cavity. At 200 µl min−1, filtering of the aerosol took place inside the TISIS, and its cavity performed as an actual spray chamber. The results, corresponding to the determination of the tertiary aerosols, demonstrated that the injector played a more important role for the TISIS than for the Cinnabar spray chamber. The ICP-AES sensitivities and limits of detection reached with the TISIS were of the same order as those found for the Cinnabar and better than those obtained for the double pass spray chamber. Wash out times for TISIS depended on the cavity/chamber inner volume. At 20 µl min−1, for a 20 cm3 volume, they were similar to those for the Cinnabar, whereas for the 9 cm3 volume, they were about 30 s shorter. In all cases, the wash out times for the TISIS were lower than those for the double pass spray chamber. The matrix, steady state effects were evaluated for nitric and sulfuric acid solutions, and the non--spectroscopic interferences for the TISIS were found to be less severe than those for both the Cinnabar and the double pass spray chamber.

Noise characteristics and analytical precision of a direct injection high efficiency and micro concentric nebuliser for sample introduction in inductively coupled plasma mass spectrometry

Noise power spectra and analytical precision data were generated and compared for a direct injection high efficiency nebuliser, DIHEN, and a micro concentric nebuliser, MCN, combined with a double pass or cyclone spray chamber for sample introduction in inductively coupled plasma mass spectrometry, ICP-MS. The different systems were compared using liquid flow rates of 85 or 100 µL min−1. Steady-state signals for 115In+ and steady-state isotope ratio measurements for 107Ag+/109Ag+ were chosen for the investigation. For background and shot noise limited precision the DIHEN was found to give better precision than the double pass spray chamber system due to higher sensitivity. For flicker noise limited precision it was found that white noise and pump interference noise were higher, and 1/f noise and mains power interference noise were lower, for the DIHEN compared to the spray chamber systems. As a result of this, for 115In+ measurements, the DIHEN gave 2–9 times higher relative standard deviation, RSD, at measurement frequencies above 1 Hz but slightly lower RSD (not statistically significant) at frequencies below 0.1 Hz compared to the conventional systems. For the isotope ratio measurements, due to the high white noise level, the DIHEN generally gave poorer precision compared to the double pass spray chamber system. To convincingly explain the rationale for the observed flicker noise limited precision data, the effect of different noise components on analytical precision was evaluated. This study made obvious the relationship between precision and different noise components visualised in noise power spectra. Such information is useful for rational optimisation of operating conditions and technical developments of instrumentation. The mathematical simulation procedure used for this study was also applied to experimental data to predict analytical precision at typical measurement frequencies.

New torch design with an in-built chamber for liquid sample analysis by ICP-AES

The analytical performance of the torch integrated sample introduction system (TISIS) for the analysis of very low sample volumes by ICP-AES is described. The TISIS consists of a commercially available torch with a low inner volume cavity (i.e., 5–9 cm3) placed at its base, which is attached to the shortened plasma injector tube through a special PTFE adapter. The nebulizer is vertically fitted to the torch base by means of a home-made Teflon adapter that has an exit for the drain solution. The aerosol is thus generated at the base of the TISIS cavity. The nebulization conditions corresponded to very low liquid flow rates (i.e., from 5 to 200 µl min−1) and conventional gas flow rates (i.e., 0.7 l min−1). Based on previously published work, these nebulization conditions favored aerosol solvent evaporation. At ambient temperature and below 40 µl min−1, almost all the solvent was evaporated and no drain was needed. Therefore, the main purpose of the TISIS cavity was to promote efficient solvent evaporation (instead of selecting the maximum drop size introduced into the plasma) and to simplify the transport path. In order to enhance solvent evaporation, the primary aerosols must be as fine as possible. In the present work, two pneumatic micronebulizers were employed: a so-called high efficiency nebulizer (HEN) and a MicroMist. For the sake of comparison, the HEN was coupled to a double-pass spray chamber and the MicroMist to a cyclonic type spray chamber. The results indicated that the TISIS exhibited promising behavior in ICP-AES, giving rise to emission intensities similar to or higher than both conventional reference systems. No further deterioration of the plasma thermal characteristics was observed when using the TISIS with respect to conventional chambers. The signal stability and limits of detection were similar for the different systems employed.

Comparison of several spray chambers operating at very low liquid flow rates in inductively coupled plasma atomic emission spectrometry.

Four different spray chambers were evaluated in ICP-AES at very low liquid flow rates: a double-pass (Scott type), a conventional cyclonic, and two low-volume cyclonic-type spray chambers (i.e., Cinnabar and Genie). A glass concentric pneumatic micro nebulizer (Atom Mist) was used in conjunction with all four chambers. The liquid flow rate was varied from 10 to 160 microL min(-1). The conventional cyclonic spray chamber gave rise to coarser tertiary aerosols, higher analyte and solvent transport rates, higher sensitivity and lower limits of detection than the remaining ones. The low-volume spray chambers afforded analytical figures of merit similar to the double-pass one, despite their very different designs. However, these spray chambers exhibited shorter wash-out times. The matrix effects were significant only for the double-pass. This fact allowed the analysis of reference samples by employing aqueous standards at a minimum level of sample consumption. The recoveries obtained for the cyclonic spray chambers and several certified samples were close to 100%, being always lower in the case of the double-pass spray chamber.